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What Part Of The Brain Controls Sleep And Wake Cycle

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What Happens When Circadian Rhythm Is Off

Neurobiology of Sleep – Circadian Rhythms, Sleep-Wake Cycle and Insomnia

When circadian rhythm is thrown off, it means that the bodys systems dont function optimally.

A distrubed sleep-wake circadian rhythm can give rise to serious sleeping problems. Without the proper signaling from the bodys internal clock, a person can struggle to fall asleep, wake up during the night, or be unable to sleep as long as they want into the morning. Their total sleep can be reduced, and a disrupted circadian rhythm can also mean shallower, fragmented, and lower-quality sleep.

In addition, studies have identified circadian rhythm disruptions as potential contributors to obstructive sleep apnea , a sleep disorder marked by repeated lapses in breathing. OSA reduces the bodys oxygen levels and causes numerous sleep interruptions through the night.

As a whole, a misaligned circadian rhythm can negatively affect sleep in many ways, increasing a persons risk of insomnia and excessive daytime sleepiness. Given the essential role of sleep for productivity and overall health, there are often significant consequences when a persons circadian rhythm is off.

V Sleep Loss And Cognition

In humans, sleep loss/disruption alters cognition and performance in a wide variety of behavioral domains including attention/vigilance, executive function, emotional reactivity, memory formation, decision making, risk taking behavior, and judgment . In addition, a substantial body of literature supports the intuitive notion that a good night√Ęs sleep can facilitate human cognitive performance , a literature not to be covered in detail in this review. This section focuses on mechanistic aspects of sleep loss/sleep disruption. Methodological consideration related to rodent models of sleep disruption are covered in a recent review .

Subtle Chemical Changes In Brain Can Alter Sleep

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  • Subtle Chemical Changes in Brain Can Alter Sleep-Wake Cycle

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The study, which focuses on a collection of ions that reside in the cerebral spinal fluid , found that not only do these changes play a key role in stimulating or dampening the activity of nerve cells, but they also appear to alter cell volume causing brain cells to shrink while we sleep, a process that facilitates the removal of waste.

Understanding what drives arousal is essential to deciphering consciousness and the lack thereof during sleep, said Maiken Nedergaard, M.D., D.M.Sc., co-director of the University of Rochester Center for Translational Neuromedicine and lead author of the study. We found that the transition from wakefulness to sleep is accompanied by a marked and sustained change in the concentration of key extracellular ions and the volume of the extracellular space.

The current scientific consensus is that the brain is woken up by a set of neurotransmitters which include compounds such as acetylcholine, hypocretin, histamine, serotonin, noradrenaline, and dopamine that originate from structures deep within the brain and the brain stem. This cocktail of chemical messengers serve to activate or arouse a set of neurons in the cerebral cortex and other parts of the brain responsible for memory, thinking, and learning, placing the brain in a state of wakefulness.

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The Brainstem Control Of State Stability

The reciprocal inhibitory exchange between the major ascending monoaminergic arousal groups and the sleep-inducing VLPO acts as a feedback loop when monoamine nuclei discharge intensively during wakefulness, they inhibit the VLPO, and when VLPO fire rapidly during sleep, block the discharge of the monoamine cell groups . This relationship is described as a bistable, flip-flopcircuit, in which the two halves of the circuit strongly inhibit each other to produce two stable discharge patterns on or off . Intermediate states that might be partially on and off are resisted. This model helps clarify why sleep-wake transitions are relatively abrupt and mammals spend only about 1% to 2% of the day in a transitional state . Hence, changes between sleep and arousal occur infrequently and rapidly. As will be described below, the neural circuitry forming the sleep switch contrasts with homeostatic and circadian inputs, which are continuously and slowly modified .

A schematic diagram of the flip-flop switch model. Adapted from Saper 2005, pg 1259 .

Historical Development Of The Stages Model

Lecture 7 physiology of the nervous system

The stages of sleep were first described in 1937 by Alfred Lee Loomis and his coworkers, who separated the different electroencephalography features of sleep into five levels , representing the spectrum from wakefulness to deep sleep. In 1953, REM sleep was discovered as distinct, and thus William C. Dement and Nathaniel Kleitman reclassified sleep into four NREM stages and REM. The staging criteria were standardized in 1968 by Allan Rechtschaffen and Anthony Kales in the “R& K sleep scoring manual.”

In the R& K standard, NREM sleep was divided into four stages, with slow-wave sleep comprising stages 3 and 4. In stage 3, delta waves made up less than 50% of the total wave patterns, while they made up more than 50% in stage 4. Furthermore, REM sleep was sometimes referred to as stage 5. In 2004, the AASM commissioned the AASM Visual Scoring Task Force to review the R& K scoring system. The review resulted in several changes, the most significant being the combination of stages 3 and 4 into Stage N3. The revised scoring was published in 2007 as The AASM Manual for the Scoring of Sleep and Associated Events. Arousals, respiratory, cardiac, and movement events were also added.

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How Does Circadian Rhythm Affect Sleep

When people talk about circadian rhythm, its most often in the context of sleep. The sleep-wake cycle is one of the most clear and critical examples of the importance of circadian rhythms.

During the day, light exposure causes the master clock to send signals that generate alertness and help keep us awake and active. As night falls, the master clock initiates the production of melatonin, a hormone that promotes sleep, and then keeps transmitting signals that help us stay asleep through the night.

In this way, our circadian rhythm aligns our sleep and wakefulness with day and night to create a stable cycle of restorative rest that enables increased daytime activity.

Dhomeostatic And Circadian Sleep Regulation

The sleep/wake cycle is not solely under circadian control. Homeostatic regulatory mechanisms pose another important influence on sleep-propensity. Sleep propensity clearly builds up when the time spent awake increases. Furthermore, an extended period of wakefulness is followed by a compensatory increase of sleep afterward. Several experimental paradigms have been developed to disentangle the circadian and homeostatic contributions to sleep regulation. Examples include constant routine studies in which the influence of environmental and behavioral factors are kept as constant as possible over the experimental period, so that the 24-hour variation measured in a variable can be attributed mainly to the endogenous pacemaker. Forced desynchrony studies use a sleep/wake schedule with a period clearly different from 24 hours that is forced upon the subjects, under constant dim-light conditions that do not entrain the circadian pacemaker. In this paradigm there is an increasing loss of synchronization between the rhythms imposed by the circadian pacemaker and the artificially induced sleep/wake cycle. This makes it possible to determine the influence of both circadian and homeostatic processes on a certain variable under study.

W.R. Pigeon, M.A. Grandner, in, 2013

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F Other Sleep Muscle Tone

1. REM sleep behavior disorder

REM sleep behavior disorder is a human manifestation of the syndrome originally observed in cats following large lesions of the brain stem reticular formation including sites involved in muscle atonia . Sporadic cases can also be observed in cats and dogs without experimenter-induced lesions . This disorder was first formally described in humans in a landmark study by Schenck, Mahowald and colleagues in 1986 and has a reported prevalence of 0.5% . RBD involves uncontrolled movements and muscular expression of dream sequences leading to sleep fragmentation and injury to patients and their sleeping partners . In the sleep laboratory such activity is correlated with enhanced EMG activity during sleep, whereas other aspects of REM sleep are normal. It is more common in people aged over 50 years old and affects more men than women. Acute RBD can be induced by various medications , whereas the cause of the chronic form is unknown. The acute form of RBD is managed by withdrawal of the offending medication, whereas the chronic form can be well managed symptomatically by clonazepam or melatonin treatment prior to bedtime .

2. Restless legs syndrome

A) Pathogenesis of Rls
B) Treatment and Animal Models of Rls

3. Periodic limb movements

4. Other disorders of motor control during sleep

Inappropriate activation of motor programs during sleep also occurs in bruxism , sleepwalking , nocturnal sleep-related eating disorder , and sexsomnia .

What Impacts Circadian Rhythms

Episode 1 – Reticular System (Sleep/Wake Part)- Project Neuroscience – Clinical Touch

Circadian rhythms are impacted by both internal and external factors . Circadian rhythm-related sleep disorders that originate within the body are called intrinsic circadian sleep disorders. Those that originate from outside the body are often referred to as circadian rhythm disorders.

Age

As infants and children age, the sleep-wake schedule shifts, and the needed amount of sleep tapers off. Infants, for example, need between 12 to 16 hours of sleep each day, while school-aged children need nine to 12 hours. Adults should aim to get between seven to nine hours of restful sleep each night.

Many teenagers experience a sleep-phase delay , in which their brain doesnt start producing melatonin until late in the evening. Late nights paired with early school wake-up times can take a significant toll on mental health and make it hard to stay focused.

Blue Light Exposure

Blue light waves are found in fluorescent and LED lights and electronic screens, such as phones, laptops, and television. Exposure to blue light waves at times when the brain should be producing melatonin, which is in the evening for most people, can halt the process and ultimately shift the circadian rhythm. As a result, blue light exposure can make falling asleep more difficult.

Jet Lag and Daylight Saving Time

Crossing two or more time zones can result in jet lag , a sleep-wake disorder that occurs when the body’s internal clock is aligned with the timezone of origin and doesnt match that of the new location.

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Neurotransmitters And Your Sleep

Some neurotransmitters help your body recharge while you sleep. They can even help you to remember things that you learned, heard, or saw while you were awake. The neurotransmitter acetylcholine is at its strongest both during REM sleep and while you are awake. It seems to help your brain keep information gathered while you are awake. It then sets that information as you sleep. So if you study or learn new information in the hours before bed, “sleeping on it” can help you remember it.

Other neurotransmitters may work against you as you sleep. Abnormalities with the neurotransmitter dopamine may trigger sleep disorders such as restless legs syndrome.

Even losing just 1 hour of sleep over a few days can have an effect. It can lead to a decrease in performance, mood, and thinking. Getting regular, adequate amounts of sleep is important. It can help you feel awake and refreshed during the day. It can also help you feel relaxed and sleepy at night. This helps make you ready for a long, restful night of sleep.

Coordinated Output Of Sleep And Wakefulness

Ascending models of arousal have terminal targets, typically in the cortex, to produce a singular behavioral output. In the layered control architecture, each layer produces a separate output that is integrated at the level of the organism. For producing consolidated sleep and wake behaviors, the relationship between sleep-active and wake-active neurons is reflected in the firing activity patterns during sleep, wake, and the transition states. Arousal neuron firing increases prior to wake onset and decreases prior to sleep onset. Sleep-active neurons, on the other hand, lag in their response in firingthis suggest that the arousal neurons act first followed by sleep-active neurons .

The relationship between sleep-active and wake-active neural populations suggests that arousal systems not only drive wakefulness but also permit sleep by deactivating arousal systems. Sleep systems, by suppressing arousal systems, elongate sleep after initiation. Strong sensory stimulation promotes arousal, while lack of sensory inputs may combine with inputs from sleep-active neurons to promote sleep. The link between regulatory elements and arousal is also reflected in the neuroanatomic overlap between sensory inputs and wake-promoting circuits. For example, the PB receives spinal cord sensory and gut visceral inputs as well as auditory and visual inputs, whereas none of the known sleep-active nodes receive direct sensory inputs.

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How Does The Brain Work

The brain sends and receives chemical and electrical signals throughout the body. Different signals control different processes, and your brain interprets each. Some make you feel tired, for example, while others make you feel pain.

Some messages are kept within the brain, while others are relayed through the spine and across the bodys vast network of nerves to distant extremities. To do this, the central nervous system relies on billions of neurons .

Sleep Drive And Your Body Clock

Nervous system

    Have you ever noticed that you feel more alert at certain times of day, and feel more tired at other times? Those patterns are a result of two body systems: sleep/wake homeostasis and your circadian rhythm, or internal body clock. These systems determine your sleep drive, or your bodys need for sleep, at any given time.

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    Single Area Of The Brain Wakes You Up And Puts You To Sleep

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    Does Melatonin Affect Rem Sleep

    Melatonin did not shift circadian phase or suppress temperature but did increase REM sleep continuity and promote decline in rectal temperature during sleep. These results were confirmed in patients who received melatonin in the second study (REM sleep percentage baseline/placebo/melatonin, 14.

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    Homeostatic Regulation Of Sleep

    Sleep is understood to be restorative, but precisely what is being restored is uncertain. As a homeostatic process, sleep allows the body to return to equilibrium when it is disturbed. For instance, sleep deprivation tends to be followed by extra compensatory sleep to make up for the loss, albeit not on a minute-for-minute basis. Borbely and colleagues proposed a two-process model of sleep regulation to explain the homeostatic and circadian drives for sleep . The homeostatic component, named Process S , is believed to derive from a substrate or protein that registers a homeostatic need to sleep during periods of extended wakefulness that is subsequently relieved during sleep. As NREM sleep appears to take precedence over REM sleep following acute sleep loss, it is probable that the homeostatic mechanisms for the two sleep states differ .

    Motivational Regulation Of Sleep/wake States

    The Sleep Wake Cycle: Circadian rhythm – Biological Psychology [AQA ALevel]

    Motivational processes can powerfully modulate the propensity of animals to stay awake or go to sleep. When motivated, humans can stay awake and engage in various cognitive and physical activities, such as reading a book, working on a grant, or attending a party, far beyond their physiological bedtime while ignoring homeostatic and circadian sleep drives. In the wild, foraging and mating opportunities and the presence of predators drive motivational responses and modulate arousal. Animals can stay awake for extended periods, sleep longer, sleep lighter, or only with half of the brain in response to different internal and external conditions. A better understanding of the processes modulating the propensity to stay awake or go to sleep will not only improve our understanding of brain circuits regulating arousal states but also provide valuable insights into the general problem of balancing conflicting needs.

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    Lobes Of The Brain And What They Control

    Each brain hemisphere has four sections, called lobes: frontal, parietal, temporal and occipital. Each lobe controls specific functions.

    • Frontal lobe. The largest lobe of the brain, located in the front of the head, the frontal lobe is involved in personality characteristics, decision-making and movement. Recognition of smell usually involves parts of the frontal lobe. The frontal lobe contains Brocas area, which is associated with speech ability.
    • Parietal lobe. The middle part of the brain, the parietal lobe helps a person identify objects and understand spatial relationships . The parietal lobe is also involved in interpreting pain and touch in the body. The parietal lobe houses Wernickes area, which helps the brain understand spoken language.
    • Occipital lobe. The occipital lobe is the back part of the brain that is involved with vision.
    • Temporal lobe. The sides of the brain, temporal lobes are involved in short-term memory, speech, musical rhythm and some degree of smell recognition.

    A Single Control Center For Sleep And Wake In The Brain

    by University of Bern

    Until now, it was thought that multiple brain areas were needed to control sleep and wakefulness. Neuroscientists from Bern have now identified one single control center for the sleep-wake cycle in the brain. The findings are of great importance for finding new sleep therapies.

    Every night we spend several hours asleep and every morning we awaken to go about our lives. How brain circuits control this sleep-wake cycle remains a mystery. Our sleep is divided into two phases, non-rapid eye movement sleep, and REM sleep during which most of our dreaming occurs. Important brain circuits have been identified using both experimental and clinical evidence, yet the precise underlying mechanisms, such as the onset, maintenance and termination of sleep and dreaming, is not well understood.

    In an important new study, neuroscientists at the Department of BioMedical Research at the University of Bern and the Department of Neurology at Inselspital, Bern University Hospital, found that neurons in the thalamus, a central hub of the brain, control sleep as well as wakefulness. The thalamus is connected to almost all other brain areas and supports important brain functions including attention, sensory perception, cognition and consciousness.

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